std array - too many initializers

Question

I don't understand why it says "too many initializers" here

#include <iostream>
#include <array>

typedef std::array<std::array<double, 3>, 3> matrix;

int main()
{
  matrix mat = {
      { 1.0, 0.0, 472.3672 },
      { 1.0, 0.0, 472.3672 },
      { 1.0, 0.0, 472.3672 }
    };
}

where am I getting wrong?